D-c voltage control with adjustable pulse width and repetition rate

ABSTRACT

A d-c voltage control circuit provides a controlled rectifier in series with a motor and battery and provides gating pulses to fire the controlled rectifier at an adjustable pulse repetition rate. A turn-off circuit for turning off the controlled rectifier is adjustable independently of the pulse repetition rate adjustment to adjust the length of time the controlled rectifier conducts after firing.

United States Patent [1 1 Yurick June 26, 1973 D-C VOLTAGE CONTROL WITHADJUSTABLE PULSE WIDTH AND REPETITION RATE [75] Inventor: John J.Yurick, Fountain Valley,

Calif.

[73] Assignee: International Rectifier Corporation, Los Angeles, Calif.

[22] Filed: May 13, 1971 [21] Appl. No.: 143,111

[52] US. Cl. 321/45 C, 318/227 [51] Int. Cl. H02m 3/32 [58] Field ofSearch 323/DIG. l;

[56] References Cited UNITED STATES PATENTS Jakobsen 321/45 C Menard321/45 C 3,568,021 3/1971 Tumbill 321/45 C FOREIGN PATENTS ORAPPLICATIONS 1,060,317 3/1967 Great Britain 321/45 C 1,912,843 10/1970Germany 321/45 C 68,553 8/1969 Germany 321/45 C 1,063,733 3/1967 GreatBritain t. 321/45 C Primary Examiner-Gerald Goldberg Att0rneyOstrolenk,Faber, Gerb & Soffen [57] ABSTRACT A d-c voltage control circuitprovides a controlled rectifier in series with a motor and battery andprovides gating pulses to fire the controlled rectifier at an adjustablepulse repetition rate. A tum-off circuit for turning off the controlledrectifier is adjustable independently of the pulse repetition rateadjustment to adjust the length of time the controlled rectifierconducts after firing.

2 Claims, 1 Drawing Figure D-C VOLTAGE CONTROL WITH ADJUSTABLE PULSEWIDTH AND REPETITION RATE SUMMARY OF THE INVENTION This inventionrelates to a solid state control circuit for d-c voltage operatedvehicles, and more particularly relates to a control circuit whichprovides full range control with simple, low-cost circuitry.

Control circuits using controlled rectifiers to vary the speed of thed-c motor of battery-operated vehicles are well known. Thus, suchcircuits are in common use for battery-operated lift trucks, and thelike. Such controls, however, have been expensive and complex and arenot well suited to use with smaller electrical vehicles such as golfcarts, small in-plant personnel carriers, and the like. The presentinvention provides a novel control circuit which provides full rangecontrol with simple lowcost circuitry. Thus, the control of the presentinvention can be used for the control of large d-c powered equipment,but also makes electric control economically feasible for smallerequipment as well.

The novel circuit of the invention provides high efficiency, increasedreliability as a result of a reduced number of components, and operationby either or both a frequency control or pulse width control. Moreover,the control is made independent of motor characteristics.

The novel circuit provides two independent but synchronized timingcircuits for gating and turning off the main controlled rectifier. Agating circuit logic is then provided which allows the power controlledrectifier to be controlled to full conduction, with the turn-off circuitbeing rendered inoperative at this adjustment.

BRIEF DESCRIPTION OF THE DRAWING The drawing shows a circuit diagram ofa preferred embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to thedrawing, there is shown a d-c motor having an armature 11 and fieldwinding 12 where motor 10 is to be energized from battery 13, throughprotective fuse 14. Clearly, any type d-c motor could be used, andbattery 13 could be any type d-c source. A main controlled rectifier 15is provided to permit energization of motor 10 from battery 13 so longas controlled rectifier 15 is conductive. The conduction of controlledrectifier 15 is controlled, in turn, by auxiliary controlled rectifiersl6 and 17.

Controlled rectifier 16 is gated at the same time as controlledrectifier 15, as will be later seen, and is connected in closed serieswith fuse 18, fuse 14, and capacitor 20. Controlled rectifier 17operates to turn off controlled rectifier 15 upon firing of controlledrectifier 17.

An inductor 21 and diode 22 are provided to allow the circuit to operatewith the motor 10 disconnected. Thus, motor 10 may be provided with aswitch 19. When this switch is opened, the inductor 21 and diode 22define a discharge path for capacitor 20, as will be later described.

Two timing control circuits 30 and 31 are then provided for controllingthe pulse repetition rate and the on-to-off ratio, respectively, ofcontrolled rectifier 15.

Control voltage for timing circuit 30 is obtained from battery 13through diode 32 and resistor 33 and is applied to storage capacitor 34and resistor 35. A reference voltage diode 36 provides a referencevoltage to the timing circuit including adjustable resistor 37 andcapacitor 38. The adjustment of resistor 37 will determine the rate atwhich capacitor 38 will charge, thereby regulating the discharge rate ofunijunction transistor 39. The pulse current output of unijunctiontransistor 39 is amplified in the amplifier consisting of transistors40, 41, 42 and 43. The output of transistor 43 is then connected in thegating circuit of controlled rectifier 15, while the output oftransistor 42 is simultaneously applied to the gating circuit ofcontrolled rectifier 16. Thus, timing circuit 30 will cause a gatingsignal to be applied to the gating circuits of controlled rectifiers 15and 16 at a frequency controlled by the adjustment of adjustableresistor 37.

Timing control circuit 31, in accordance with an important feature ofthe invention, derives its operating voltage from capacitor 20 throughresistor 50. Circuit 31 includes a capacitor 51 in parallel withreference diode 52 and a timing R-C circuit including adjustableresistor 53 and capacitor 54. The adjustment of resistor 53 determinesthe time at which unijunction transistor 55 will conduct a current pulse(following the charging of capacitor 20) for gating controlled rectifier56. The output of controlled rectifier 56 is connected to the gatecircuit of controlled rectifier 17 as shown. As will be later seen, theadjustment of resistor 53 determines the time at which controlledrectifier l7 fires to stop conduction of controlled rectifier 15,thereby to conduct the on-to-off ratio of controlled rectifier 15.

The operation of the circuit is as follows:

In order to vary the speed of d-c motor 10, and thus the load which itdrives, controlled rectifier 15 is switched on and off at a controlledrate and for a controlled duration, thereby controlling the averagevoltage applied to motor 10.

Assume first that controlled rectifier 15 is nonconductive and thecircuit to battery 13 is closed. Capacitor 38 of timing circuit 30begins to charge until after a given time, determined by the values ofadjustable resistor 37 and capacitor 38, transistor 39 discharges apulse of current. This pulse is amplified by transistors 40, 41, 42 and43 to apply current pulses to the gate circuits of controlled rectifiers15 and 16. Both controlled rectifiers 15 and 16 become conductivewhereby motor 10 is connected to battery 13, and capacitor 20 is chargedfrom battery 13, through controlled rectifier 16.

Motor current now begins to flow, and capacitor 20 charges to applyinput voltage to timing circuit 31. Thus, the timing circuit includingresistor 53 and capacitor 54 begins to conduct with the unijunctiontransistor 55 conducting a current pulse at a time dependent upon theadjusted time constant of the R-C circuit formed by elements 53 and 54.This delivers a gate pulse to fire controlled rectifier 56 which, inturn, discharges capacitor 51 into the gate circuit of controlledrectifier 17 to fire controlled rectifier 17.

When controlled rectifier 17 is gated, charged capacitor 20 reverses thevoltage across controlled rectifier 15 to stop conduction of controlledrectifier 15, thereby terminating the current pulse applied to motor 10.Note that the length of this pulse depends upon the setting ofadjustable resistor 53.

During this time, capacitor 38 in timing circuit 30 has been chargingand, at some predetermined time, fires transistor 39, again to gatecontrolled rectifiers l5 and 16. The adjusted time constant of resistor37 and capacitor 38, therefore, determines the pulse repetition rate forpulses which are applied to motor 10.

It will be noted that the circuit described above can control outputvoltage to motor in a constant pulse width, variable repetition ratemode, or in a constant repetition, variable pulse width mode, or in somecombination of these two modes.

Several significant features should be noted concerning the operation ofthe novel circuit.

First, it will be seen that the various controlled rectifiers areoperated without using conventional pulse transformers.

Second, there is a novel interrelation between circuits 30 and 31 whichcauses positive synchronization of turn-on and turn-off of controlledrectifier by operating transistor 55 from the voltage on commutatingcapacitor 20.

The novel circuit further permits full conduction of controlledrectifier 15 simply by removing the gate pulse applied to controlledrectifier 16. This can be obtained by suitable adjustment, or opening ofthe R-C circuit including resistor 37 and capacitor 38, or by simplyshorting the gate of controlled rectifier 17 to its cathode.

An important advantage of the circuit of the invention is that thecontrol system can continue to operate even if the motor circuit isopened as by the opening of switch 19. Such continued operation of thecontrol circuit is desirable for many different purposes and isunrelated to the type of motor being used. In this mode of operation,the capacitor 20 charges in the usual manner with the firing ofcontrolled rectifiers l5 and 16. With the firing of controlled rectifier17, capacitor 20 can now discharge through the circuit includinginductor 21, diode 22 and the main electrodes of controlled rectifier 17rather than discharging through the motor 10 when the motor isconnected.

Although this invention has been described with respect to its preferredembodiments, it should be understood that many variations andmodifications will now be obvious to thos skilled in the art, and it ispreferred, therefore, that the scope of the invention be limited not bythe specific disclosure herein, but only by the appended claims.

I claim:

I. A d-c voltage control circuit comprising, in combination:

first, second and third controlled rectifiers each having mainelectrodes, and a control electrode; source of d-c voltage, and meansfor connecting said first controlled rectifier main electrodes and saidsource of d-c voltage in series with one another and in series with aload; commutating capacitor; said commutating capacitor connected inclosed series connection with said main electrodes of said first andsecond controlled rectifiers, respectively, whereby the conduction ofsaid second controlled rectifier permits the discharge of said capacitorthrough said first controlled rectifier in a direction to extinguishcurrent flow in said first controlled rectifier; said main electrodes ofsaid third controlled rectifier connected in closed series relation withsaid source of d-c voltage and said main electrodes of said firstcontrolled rectifier, whereby conduction of said first and thirdcontrolled rectifiers causes charging of said capacitor from said sourceof d-c voltage; said main electrodes of said third controlled rectifierbeing further connected in closed series relation with said mainelectrodes of said second controlled rectifier and said source of d-cvoltage;

first firing circuit means connected to said control electrodes of saidfirst and third controlled rectifiers for applying firing pulses theretohaving a predetermined repetition rate;

and second firing circuit means connected to said control electrode ofsaid second controlled rectifier for applying firing pulses thereto apredetermined time after the firing of said first and third controlledrectifiers; said load comprising a do load; said d-c load beingconnected in a closed series relation which includes only saidcommutating capacitor and said main electrodes of said third controlledrectifier; and synchronizing circuit means connected between said firstand second firing circuit means for insuring the presence of a firingpulse from said second firing circuit means a predetermined time afterthe production 'of a pulse by said first firing circuit means; saidsynchronizing circuit means including said commutating capacitor as asource of operating voltage for said second firing circuit means.

2. The control circuit of claim l which includes first and secondindependent adjustment means for said first and second firing circuits,respectively, for independently adjusting the rate of production offiring pulses thereby.

1. A d-c voltage control circuit comprising, in combination: first,second and third controlled rectifiers each having main electrodes, anda control electrode; a source of d-c voltage, and means for connectingsaid first controlled rectifier main electrodes and said source of d-cvoltage in series with one another and in series with a load; acommutating capacitor; said commutating capacitor connected in closedseries connection with said main electrodes of said first and secondcontrolled rectifiers, respectively, whereby the conduction of saidsecond controlled rectifier permits the discharge of said capacitorthrough said first controlled rectifier in a direction to extinguishcurrent flow in said first controlled rectifier; said main electrodes ofsaid third controlled rectifier connected in closed series relation withsaid source of d-c voltage and said main electrodes of said firstcontrolled rectifier, whereby conduction of said first and thirdcontrolled rectifiers causes charging of said capacitor from said sourceof d-c voltage; said main electrodes of said third controlled rectifierbeing further connected in closed series relation with said mainelectrodes of said second controlled rectifier and said source of d-cvoltage; first firing circuit means connected to said control electrodesof said first and third controlled rectifiers for applying firing pulsesthereto having a predetermined repetition rate; and second firingcircuit means connected to said control electrode of said secondcontrolled rectifier for applying firing pulses thereto a predeterminedtime after the firing of said first and third controlled rectifiers;said load comprising a d-c load; said d-c load being connected in aclosed series relation which includes only said commutating capacitorand said main electrodes of said third controlled rectifier; andsynchronizing circuit means connected between said first anD secondfiring circuit means for insuring the presence of a firing pulse fromsaid second firing circuit means a predetermined time after theproduction of a pulse by said first firing circuit means; saidsynchronizing circuit means including said commutating capacitor as asource of operating voltage for said second firing circuit means.
 2. Thecontrol circuit of claim 1 which includes first and second independentadjustment means for said first and second firing circuits,respectively, for independently adjusting the rate of production offiring pulses thereby.